With the 2019 US Open in the books, it's time to look back at some of the biggest storylines on the men's side from the past fortnight at the USTA Billie Jean King National Tennis Center in Flushing Meadows.

New Next-Gen Torchbearer

It's been debated for a while which next gen star will be the guy to help usher in a new era after the Big 3 and become the first man born after 1990 to win a Grand Slam. Alexander Zverev looked like the obvious answer to that question for a while, but he's battling confidence issues and hasn't translated his success at Masters tournaments to the best-of-five Grand Slam format. Then, Stefanos Tsitsipas came along and beat Roger Federer in a four-set thriller at the Australian Open, but he, too, has fallen into a rut recently. While Zverev bowed out in the Round of 16 here and Tsitsipas fell in the first round, the guy who's looked like the best of the Next Gen bunch all summer became the first to reach a Grand Slam final and acquitted himself wonderfully there, falling to Rafael Nadal in a five-set thriller. Daniil Medvedev is up to No. 4 in the world after this result, which capped a 20-3 American hard-court swing for the 23-year-old Russian. With a pair of victories over Novak Djokovic among his tour-leading 50 wins this season, Medvedev has shown he has what it takes to beat the best, and it wouldn't be shocking at all if his next Grand Slam final finished with a different result.

Rafa Boosts his GOAT Case

It's pretty much universally accepted that Nadal, Djokovic and Federer in some order are the three greatest tennis players of all time, and while Greatest of All Time is a subjective title, most consider Grand Slam titles to be the gold standard in the GOAT debate. With a five-set win over Medvedev in the final for his fourth career US Open title, Nadal is now the closest he's ever been to Federer by that metric since both became Grand Slam winners, trailing Federer's all-time best total of 20 by one while holding a three-major cushion over Djokovic. Commentator and all-time great John McEnroe mentioned that perhaps the most important metric besides Grand Slam titles is year-end No. 1 finishes, and Nadal's win in Flushing pretty much ensures that he'll snag that honor for the fifth time, equaling Federer, Djokovic and Jimmy Connors at one behind Pete Sampras' all-time leading mark in that category. Nadal currently trails Djokovic by 645 ranking points but has no points to defend the rest of the year and leads by 1,940 points since the start of 2019.

Nadal's head-to-head edge over Federer, Olympic gold medal, greater degree of difficulty in Grand Slam titles and edge in Masters titles have long given him a strong argument as the GOAT anyway, but the 33-year-old Nadal is as close as he's ever been to making the debate against his 38-year-old counterpart truly one-sided. Of course, Federer has bounced back after being written off before and Djokovic might still have the brightest future of the three since 32 is the new 22 in men's tennis, so there are likely a few more chapters still yet to be written in the greatest era of the sport.

Injury Bug Keeps on Biting

Injuries have always been part of the game, but they seem to be playing an especially large role in 2019. Among notable players who couldn't participate in this tournament were 2009 US Open champion Juan Martin del Potro (kneecap), 2017 runner-up Kevin Anderson (knee) and 2016 Wimbledon finalist Milos Raonic (glute). Additionally, Djokovic had to retire against Stan Wawrinka in the fourth round due to a shoulder injury and a back injury played a part in Federer's subpar fifth-set performance during his quarterfinal defeat to Grigor Dimitrov. That's not to mention Dominic Thiem, who lost in the first round while attempting to play through an illness. Of that notable group, only Anderson has been ruled out for the remainder of 2019 while the rest could return sooner, but a lot of draws have been opening up due to notable injuries.

Berrettini's Breakout

If it wasn't for Medvedev, we'd all be talking about a different 23-year-old in Matteo Berrettini, who reached his first career Grand Slam semifinal here. The Italian lost to Nadal in straight sets, but he demonstrated notable improvement from his fourth-round Wimbledon loss to Federer, winning 11 games against Nadal after only taking five off Fed. Berrettini doesn't look ready to contend for major titles quite yet, but he's knocking on the door of the top 10 at No. 13 and is among the hardest players on tour to break.

Americans Disappoint Again

The American contingent had some nice story lines going early, but they all flamed out pretty quickly. None of the 16 American men in the draw made it past the third round, and of the three that reached that stage, John Isner was the only one to win a set. Looking forward, American hopes in the near future seem to lie with a couple of big-serving behemoths, as the 6-foot-10 Isner is looking to regain the excellent form he showed before fracturing his foot in the final of Miami in March, while 6-foot-11 Reilly Opelka – who just turned 22 – showed promise in his first career US Open appearance with a first-round win over No. 11 seed Fabio Fognini. Joining Isner (20) and Opelka (46) among Americans ranked in the top 50 are Taylor Fritz (30), Frances Tiafoe (43) and Sam Querrey (45).

Grigor Leads the Big Movers

Dimitrov picked up his first win against Federer in eight tries en route to the semifinals, and the previously slumping Bulgarian was rewarded with a 53-point climb in the rankings from 78 to 25. Other major climbers include Berrettini (up 12 spots to 13) and a pair of guys who made surprising fourth-round runs – Pablo Andujar (up 20 to 50) and Dominik Koepfer (up 32 to 86). The biggest drop was suffered by del Potro, who fell to 55 spots to 71 as his points from last year's fun to the final expired. After a magical 2018 run to the quarterfinals that included a win over Federer, John Millman lost to Nadal in the first round, resulting in a 30-spot drop to 95. Joao Sousa saw all his momentum from a fourth-round run at Wimbledon disappear, as his first-round exit here replaces last year's fourth-round US Open result, resulting in a 20-spot slide to 64.

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Sasha has been contributing NFL, NHL, NBA, MLB and Tennis content to RotoWire since 2015, with an emphasis on DFS. He is a huge New York sports fan who has been playing fantasy sports since middle school.